7005
Macromolecules 1995,28, 7005-7009
Induction of the Smectic Phase in the Polymer Complexes between Electron-Accepting Ionic Nitrostilbazoles and Electron-Donating Liquid-Crystalline Polymers Yozo Kosaka Central Research Institute, Dai Nippon Printing Company, Ltd., Ichigaya-Kagamachi, Shinjuku-ku, Tokyo 162-01, Japan
Takashi Kat0 and Toshiyuki Uryu* Institute of Industrial Science, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan Received December 16, 1994; Revised Manuscript Received June 8, 1995@
ABSTRACT: A new type of miscible polymer complex was prepared from electron-accepting trans-Nalkyl-4-nitro-4'-stilbazoliumbromides or iodides and electron-donating polymers containing a mesogenic (carbazolylmethy1ene)aniline. The 1:1 (mole ratio) polymer complexes showed smectic behavior. For example, the 1:1 polymer complex of trans-N-hexyl-4-nitro-4'-stilbazoliumbromide and the electrondonating polyacrylate exhibited a smectic A phase from 75 to 140 "C, although the smectic phase did not appear in both individual components. The isotropic temperature of these polymer complexes increased with increasing carbon number of the alkyl chain in the nitrostilbazolium bromide. Similar tendencies on the thermal behavior were observed for the complexes of the ionic nitrostilbazoles and a low-molecularweight nematic compound containing the same carbazolyl group. It was concluded that the miscibility and the induction of the smectic phases are caused by the complex formation between the ionic nitrostilbazole group and the nonionic mesogenic (carbazolylmethy1ene)anilinegroup by ionic and electron donor-acceptor interactions.
Introduction The mixing of liquid crystals has been utilized for the control of mesogenic properties for low-molecular-weight compounds and the identification of mesophases. l p 2 Recently, new classes of liquid-crystalline mixtures have been prepared through hydrogen bond^,^-^ ionic interacti~ns,~-ll and electron donor-acceptor interactions.12-21 These liquid-crystalline compounds exhibited the thermal stability and the induction of mesophases. The electron donor-acceptor interaction is one of the interactions which causes miscibility between two kinds of compounds. For example, this behavior appears when electron donor-acceptor interactions act between two kinds of compounds, i.e., one having such highly polar groups as nitro, cyano, and isothiocyanato as electron acceptors and the other having such nonpolar groups as alkyl and alkyloxy as electron donors. Liquid-crystalline polymers by electron donor-acceptor interactions were also reported on main-chain and sidechain polymer^.^^-^^ Previously, we reported that the miscibility and the induction of smectic phases in the copolymers and the blends of polymers were caused by intermolecular electron donor-acceptor interaction^.^^,^^.^^*^' Moreover, a new type of miscible liquid-crystalline complex was prepared from low-molecular-weight nonionic (carbazolylmethy1ene)anilines as the electron donor and ionic nitrostilbazoles as the electron acceptor.12 These complexes showed stable smectic phases. In this paper, we wish to report the thermal properties and the miscibility of the mixtures of electrondonating liquid-crystalline polymers with electronaccepting ionic low-molecular-weight compounds. The polymers contain a mesogenic (carbazolylmethy1ene)aniline group and the low-molecular-weightcompounds have a nitrostilbazolium group (Chart 1). The liquidAbstract published in Advance ACS Abstracts, September 1, 1995. @
Chart 1. Molecular Structures of (A) Electron-Accepting nXSzNOz and (B) Electron-Donating HCMA, PABCz, and PM6Cz
(A) Electron-accepting compounds
nXSzN02 n: 5-10; X CI, Br, or I SzN02: nltrostilbazolegroup
(6) Electron-donating compounds CH3
HCMA (K 91 N 122 I)
?
R = H: PA6Cz (g 69 N 169 I)
CH3: PM6Cz (g 79 N 172 I)
crystalline properties of the mixtures of low-molecularweight ionic compounds with mesogenic compounds were also examined. These mixtures were characterized by optical polarizing microscopy, differential scanning calorimetry, and X-ray difiactometry.
0024-9297/95/2228-7005$09.00/0 0 1995 American Chemical Society
7006 Kosaka et al.
Macromolecules, Vol. 28, No. 20, 1995
Table 1. Thermal Properties of t r a n e - N - ~ ~ l - 4 - n i t r o - 4 'Halides - s t ~ b(~n o X~ S~ zN02~)~ n X phase transition tempb ("C) M i c (kJ/mol) 5 Br K 146 I C1 K 129 SA 190 I 4.8 6 Br K 149 I 6 6 1 K 193 Id 7 Br K 146 SA 168 I 6.7 8 Br K 170 SA 175 I 5.8 9 Br K 154 SA 175 I 5.1 10 c1 K 167 SA 227 Id 6.2d 10 Br K 175 SA 186 I 4.7 10 I K 147 I a Reference 12. Transition temperature ("C) determined by DSC at 10 deg/min on the first (6ISzN02 and 10ClSzN02) and the second heating rungs and by microscopic observation. K crystalline. SA: smectic A. I: isotropic. Measured by DSC. Mi: enthalpy change in the clearing. Partial decomposition observed.
Temperature ("C)
Figure 1. DSC thermograms of the 1 : l binary mixtures of (A) 6ClSzN02 with HCMA, (B) 6BrSzN02 with HCMA, and (C) 6ISzN02 with HCMA on the second heating run at 10 deg/ min .
Results and Discussion Thermal Properties of Binary Mixtures of LowMolecular-Weight Compounds, nXSzNOa and HCMk trans-N-Alkyl-4-nitro-4'-stilbazolium halides (nXSzN02, n = 5-10; X = C1, Br, I; SzN02, nitrostilbazole group)12and 4-(hexyloxy)-N-[(9-methyl8-carbazolyl)methylenelaniline (HCMAl2Owere chosen as ionic electron-accepting and as nonionic electron-donating compounds, respectively. The molecular structures and the thermal properties of these compounds are shown in Chart 1 and Table 1. The binary mixture of nXSzNO2 with HCMA were prepared by evaporation of chloroform solutions of these mixtures. The DSC thermograms of the 1:l(mole ratio) binary mixtures of HCMA with 6XSzNO2 having chloride, bromide, or iodide as a halide are given in Figure 1. For the binary mixture of 6ClSzN02 with HCMA, crystallization did not occur on the first cooling. On the
Table 2. Thermal Properties of the 1:l Binary Mixtures of tm~-N-AUryl-l-nitro-4'-stilbazoliumHalides with (D-methyl-2-carbazolyl)methylene]aniline 4-(Hexyloxy)-N-[ (nXSzNOa-HCMA) 1:l mixture phase transition tempa ("C) AH? (kJ/mol) 6ClSzN02-HCMA phase separation 6BrSzN02-HCMA K 83 SA 149 1 2.9 6ISzN02-HCMA K 96 SA 118 1 2.2 1OClSzN02-HMA phase separation 10BrSzN02-HCMA K 88 SA 168 1 3.5 10ISzN02-HCMA K 107 SA 150 I 3.3 a Transition temperature ("C) determined by DSC at 10 deg/ min on the second heating run and by microscopic observation. K crystalline. SA: smectic A. I: isotropic. Measured by DSC. Mi: enthalpy change in the clearing.
second heating, an exotherm peak corresponding to the crystallization of HCMA and endotherm peaks due to the meltings and the isotropizations were observed for the mixture (Figure 1A). The endotherm peaks at 122 (Til)and 188 "C (Ti2) may correspond to the isotropic transitions of individual components, taking into account the microscope observation. These results suggest that the mixture caused phase separation. On the other hand, for the 1:l binary mixtures of HCMA with 6BrSzN02 or 6ISzN02, crystalline-crystalline, crystalline-mesomorphic, and mesomorphic-isotropic transition peaks appeared, with no endothermic peaks originating from the individual components. These binary mixtures showed focal-conic fan and homeotropic textures on the microscopic observation, indicating that they have smectic A phases. The smectic A phases were observed from 83 to 149 "C and from 96 to 118 "C, respectively, though the smectic phase did not appear in both individual components (Table 2). A similar tendency was observed for other mixtures having different alkyl groups. For instance, the 1:l binary mixture of HCMA with lOClSzNO2 which has a decyl chain a t the terminal showed phase separation. On the contrary, the mixtures having the bromide or the iodide exhibited smectic phases from 88 to 168 "C and from 107 t o 150 "C, respectively. It is presumed that since a contact ion pair is formed between chloride and pyridinium groups by a stronger ionic interaction, the nClSzN02 acts as a weak electron acceptor which eventually holds a localized cationic charge. On the other hand, the bromide and iodide compounds containing a pyridinium group work as a stronger electron acceptor, probably because in both bromides and iodides a cationic charge is delocalized through the stilbazolium. The nBrSzN02-HCMA complex has a wider mesophase temperature range than the iodide homologue, exhibiting the formation of a more stable smectic phase. The enthalpy changes in the clearing for these complexes ranged from 2.2 to 3.5 kJ/mol. The thermal properties of the 1:l nBrSzN02-HCMA complexes are listed in Table 3. For the nBrSzNO2HCMA complexes, the transition temperatures are plotted as a function of carbon number of the alkyl chain in nBrSzNO2 (Figure 2). All complexes exhibited stable smectic phases. For example, the 5BrSzN02-HCMA complex showed a smectic phase from 98 to 135 "C, although both individual components, i.e., 5BrSzN02 and HCMA, exhibited no smectic phase. The smectic phase was observed from 88 t o 168 "C for the 10BrSzN02-HCMA complex. The isotropic temperature of these complexes increased with increasing carbon number of the alkyl chain in nBrSzNO2. These isotropic temperatures were approximately 15 deg higher than the calculated value based on the proportion of the individual components. The odd-even effect was
Macmmolecules, Vol. 28, No.20. 1995
Smectic Phase Induction in Polymer Complexes 7007
Table S. T h e d Pmpertien of the k1 Complexen of hPnr-N-Alkyl-4.nihlbamlium Bromides with ~He~lo.y~-N-I~~methyhyl-2earbazolyl~methylenelanil~e (nBrSzNOs-HCMA)
1:l mmolex 5BrSzNa-HCMA
6BrSzN02-HCMA lBrSzN02-HCMA
1 7 , 50
nhase transition t e m d (OC) AH+ fkJlmol) K 9 8 SA 135 I 3.3 K 8 3 SA 149 I 2.9 K 112 SA 160 I 3.7
1w
TI 1 M
Temperature ("C)
Transition temperature (T)determined by DSC at 10 de@ min on the m n d heating run and by microscopic observation. K crystalline. SA: 8mectic A 1. isotropic. Measured by DSC. AH; enthalpy change in the clearing. I
K
SO^"""^ S
6
7
8
0
10
n
Figure 2. Dependence of the transition temperatures on the carbon number of the alkyl chain in nBrSzN02 for the 11 nBrSzNOrHCMA complexes.
IBI
Table 4. Thermal F'roprtien of the kl Polymer Mixtwea of hPnr-N-Alky14nibo-I'stllbaxolium Halides with PolyI~4~IB-~acryloylo.y~h~lloxyl-N-I~~methyl-2carbazolyl)methylenelanilinel(nXSzNOs-PABCz)
6ISzNO
lOCISzN02-PA6Cz IOBrSzNOz-PA6Cz
0.5
phase separation g 69 SA 168 I g65 SA 140 1
2.0
101SzNOrPA6Cz 2.0 Transition temperature ("C) determined by DSC at 10 de# min on the second heating run and by microscopic observation. g: glassy. SA: smectic k N nematic. I: isotropic. Measured by DSC. AHt: enthalpy change in the clearing.
*
seen for the crystalline-smectic transition temperature for the 1:lnBrSzNOz-HCMA complexes. The enthalpy changes in the clearing for these complexes were between 2.7 and 3.7 kJ/mol and showed a n alternation tendency. LiquidCrptaUme Ropertiea of Polymeric Cornplexes of nBrSzNO, with PABCz. Poly[4-[[6-(acryloyloxy~hexylloxyl-N-[(9-methyl-2-carblylhnethylenelaniline1 ( P A ~ C Zand )~~ a polymethacrylate homologue (PM6Cz.P as electrondonating polymers showed nematic phases from 69 to 169 "C and from 79 to 172 "C, respectively (Chart 1). Thermal properties of 1:l mixtures of the polyacrylate with nXSzN02 are given in Table 4. The 1:l nXSzNOz-PA6Cz mixtures had thermal behaviors similar to those of the 1:lbinary mixtures of nXSzNO2 with monomeric HCMA. Although the nCISzNOz-PA6Cz mixtures showed phase separation, the miscible polymer mixtures were obtained when X in nXSzNOz was Br or I. In addition, in the polymer mixtures of PAGCz with 6BrSzN02 or 10ISzN02, the induction of the smectic phase was
Figure 4. Optical polarized microphotographs of the 1:l polymer mixtures of (A) 6BrSzNOz with PA6Cz at 130 "C and (B) 6BrSzN0~with PM6OMe at 120 "C on cooling.
observed. For example, the lOISzN02-PAGCz mixture exhibited a smectic phase from 65 to 140 "C. A typical mixture DSC thermogram of the 1:lGB~SZNOZ-PAGCZ showed the existence of the glass transition at 75 "C and the smectic-isotropic transition at 140 "C (Figure 3). Both microwpic and DSC studies revealed that the mixture had the miscible smectic phase (Figure 4A).No change in UV spectra of the mixture solution in chloroform was detected. However, miscible red mixtures were obtained from PAGCz with nBrSzNOz or nISzN02. The induction of the smectic phase and the miscibility revealed that the electron donor-acceptor interaction acted in the complex. On the other hand, for the 1:l polymer mixture of 6BrSzN02 with a liquid-crystalline polymethacrylate containing an electron-donating (4methoxybenzy1idene)aniline group (PM6OMe) (Chart 2),26phase separation was observed, as shown in Figure 4B.
Macromolecules, Vol. 28, No. 20, 1995
7008 Kosaka et d.
I
N+K
I
-
150
-
P E
100:
c"F E8E;1 0 0
Q
c
Y
I
5
II
I
/I:
O
7
150
-
100
-
so
-
/-/-----a
so
0
c
I
0
u 5
s
7
50
0
0.5
1
Proportion of BBrSzNO2
Figure 5. Phase diagram of the polymer mixtures of PA6Cz and 6BrSzN02 as a function of the proportion of 6BrSzN02.
8
9
i
o
-
5
0
6
8
7
9
10
n
n
Figure 6. Dependence of the transition temperatures on the carbon number of the alkyl chain in nBrSzNO2 for (A) the 1:l nBrSzN02-PAGCz complexes and (B) the 1:l nBrSzNO2-
PM6Cz complexes.
Chart 2. Molecular Structure of PM60Me QH3
PM60Me (g 56 N 123 I)
Table 5. Thermal Properties of the 1:l Polymer Complexes of truns-N-Alkyl-4-nitro-4'-stilbazolium Bromides with Poly[4-[[6-~acryloyloxy)hexylloxylN-[(9-methyl-2-carbazolyl)methylenelanilinel 1:lcomplex
(~B~S~NOB-PA~CZ) phase transition tempa ("C) Mib(kJ/mol)
SBrSzN02-PAGCz g 67 SA124 1 1.9 6BrSzN02-PAGCz g 75 SA 140 I 2.0 7BrSzN02-PAGCz g 75 SA 162 I 2.5 8BrSzN02-PAGCz g 74 SA 162 I 2.8 9BrSzN02-PAGCz g 69 SA167 1 2.5 lOBrSzN02-PAGCz g 69 SA168 1 2.0 Transition temperature ("C) determined by DSC at 10 deg/ min on the second heating run and by microscopic observation. g: glassy. SA:smectic A. I: isotropic. Measured by DSC. Mi: enthalpy change in the clearing. The phase diagram of the GBrSzNOz-PA6Cz mixtures is presented in Figure 5. When the proportion of 6BrSzN02 was over 0.75, phase separation occurred. The smectic phase was induced at near equimolar compositions. However, in this system, the thermal stability of the smectic phase was not caused, unlike the mixture of HCMA with 6 B r S ~ N 0 z . l ~ For the 1 : l nBrSzN02-PAGCz complexes, the clearing temperature increased with increasing carbon number of the alkyl chain, while the glass transition temperature did not depend on the alkyl length (Table 5 and Figure 6A). All polymer complexes exhibited smectic phases. For example, a smectic phase was observed from 74 to 162 "C for the 1:l 8BrSzN02PA6Cz complex. The enthalpy changes in the clearing for these polymer complexes were from 1.9 to 2.8 kJ/ mol. As shown in Figure 6B, similar thermal properties were seen for the 1:l polymer complexes of nBrSzNO2 with a polymethacrylate containing the same mesogenic carbazolyl group (PM6Cz). It has been reported that the 1:l polymer mixture of PM6Cz with a nonionic 4-(hexyloxy)-N-(4-nitrobenzylidenelaniline showed a nematic phase.20 Therefore, the miscibility and the induction of the smectic phase for the polymer complexes of side-chain liquid-crystal-
1.2
5
I
1
10
20
30
2 0 (dw)
Figure 7. Wide-angle X-ray diffraction pattern of the 1:l
quenched SBrSzN02-PAGCz complex film.
line polymers containing the carbazolyl group with nBrSzNOz may be caused by a combination of electron donor-acceptor and ionic interactions. The wide-angle X-ray diffraction pattern of the 1:l 5BrSzN02-PAGCz complex film quenched from the liquid-crystalline state showed three sharp reflections at small angles and a broad reflection at wide angles (Figure 7). The broad peak centered at 28 of 21.8" (d = 4.08 A) is due to the distance between the planes on which the oriented mesogenic groups lies. The lowangle diffraction was measured by a small-angle X-ray diffractometer. Three sharp reflections were observed a t 28 of 1.75" (d = 50.4 A), 3.50" (d = 25.2 A), and 5.20" (d = 17.0 A), respectively (Figure 8). The spacings of 25.2 and 17.0 A are assumed to correspond nearly to the fully-stretched molecular lengths of A6Cz (26.5 A) and 5BrSzN02 (19.5 A), respectively. And, since the spacing of 50.4 A is twice the spacing of the observed spacing of 25.2 A, the polymer side chains might be oriented to form a doubly-layered conformation. Thus, both microscopic and X-ray diffraction studies suggest that the polymer complex had a smectic A phase. The smectic layer spacings measured by small-angle X-ray diffractions for these polymer complexes increased with increasing carbon number of the alkyl chain in nBrSzNOz (Figure 9). This widening of the spacing might originate from an increase in the whole length of the complex structure which was caused by the longer alkyl chain. The smectic phase of these complexes may have a mesophase close to a bilayer structure, in which the complex is formed between nBrSzNO2 and PAGCz, as illustrated in Figure 10.
Macromolecules, Vol. 28, No. 20, 1995
Smectic Phase Induction in Polymer Complexes 7009
Figure 8. Small-angle X-ray diffraction pattern of the 1:l quenched 5BrSzN02-PA6Cz complex film.
Figure IO. Schematic illustration of a pmpOsed mesophase structure in the 5BrSzNOrPAGCz complex: (shaded ellipses) electrondonating (carbazo1ylmethylene)aniline group; (open ellipses) electron-accepting nitrostilbazolium gmup.
References and Notes (1) Gray, G. W.; Gmdby, J. W. G. Smctic Liquid Cryst&, Leonard HiU Glasgow and London, 1984. (2) Sackmann, H.; Demus, D. Z. Phys. Chem. 1983,224, 177. (3) Kato, T.;F r a e t , J. M. J. Macromolecules 1989, 22, 3818. (4) Kato, T.;Kihara, H.; Uryu, T.;Fujisbima, A,; Wchet, J. M. J. Macromolecules 1992, 25, 6836. S 8 7 I S 1 0 (5) Kumar, U.; Mchet, J. M. J.; Kato, T.;Ujiie, S.;Iimura, K. n Angew. Chem., Int. Ed. Engl. 1992,31, 1531. Figure 9. Dependence of the three spacings measured by (6) Kato, T.;Kihara, H.; Kumar, U.; Uryu, T.;Ffichet, J. M. J. small-angle X-ray diffractometry on the carbon number of the Angew. Chem., Int. Ed. Engl. 1994,33,1644. alkyl chain in nBrSzNO2 for the 1:l nBrSzNOt-PA6Cz (7) Wilson, L.M. Macromolecules 1994,27, 6683. complexes. The widest spacing (O),the middle spacing (=I, (8) Fouquey, C.; Lehn,J.-M.; Levelut, A,-M.Adv. Mater. 1990, and the narrowest spacing (A)corresponding to 28 = around 2, 254. 1.7, 3.5, and 5 2 , respectively. (9) Ujiie, S.; Tanaka,Y.; Iimura, K Chem. Lett. 1991, 1037. (10)Ujiie, S.;Iimura, K Macromolecules 1992,25, 3174. (11) Bruce, D. W.; Dunmur, D. A,; Hudson, S. A,; Lalinde, E.; Experimental Section Maitlis, P. M.; McDonald, M. P.; Orr, R.; Styring, P. Mol. Cryst. Liq. Cryst. 1991,206, 79. Materials. trans-N-~kyl-4-nitro-4'-stilb~o~um halides (12) Kosaka, Y.; Kato, T.;Uryu, T.Liq. Cryst. 1996, 18, 693. (nXSzNOd,~ e x y l ~ ) - N - [ ( 9 - m e t h y l - 2 s a r b a z o l y l ) m e (13) Park, J. W.; Bak,C. S.; Labes, M. M. J.Am. Chem. Scc.1976, aniline (HCMA), poly~4~~6~aeryloyloxy~h~lloxyl-N-l~9-meth97, 4398. yl-2-carbazolyl)methylenelanilinel(PAGCz), and poIy[4-[16(14) Araya, It; Matsunaga, Y. Bull. Chem. Sm. Jpn. ISSO, 53, (methacryloyloxy)hexylloxy1-N[(9-methyl-2-carbazolyl)3079. methylenelanilinel (PM6Cz) were prepared according to the (15) Ringsdorf, H.; Wiistefeld, R.; Zerta, E.; Ebert,M.; WendorfF, procedure previously desmibed.12~",28 J. H. Awew. Chem.. Int. Ed.Ewl. 1989.28.914. Preparation of the Polymer Mixtures of nXSzN02 (16) Moller, Tsukruk,V.;WendorffJ. H.; Be&, H.; Ringsdorf, with PABCz. Polymer mixtures of nXSzNOz with PA6Cz H.~ i qcryst. . 1992, 12, 11. were prepared by evaporation of the mixture solutions in (17) Praefeke, K; Singer,D.; Eckert, A. Liq. Cryst. 1994, 16,53. chloroform, followed by drying under vacuum. (18) Usol'tseva, N.; Praefcke, It; Singer, D.; Giindogan, B. Liq. Characterization. A differential scanning calorimeter Cryst. 1994, 16, 611. (Mettler DSC 30) was used to determine phase transition (19) Imrie, C. T.;Paterson, B. J. A. Macmmolemles 1994,27,6673. (20) Kosaka, Y.;Uryu, T.Macromolecules 1994,27,6286. temperatures using heating and cooling rates of 10 deglmin. (21) Kosaka,Y.; Uryu, T.J. Polym. Sei., Part A Polym. Chem., The peak temperature of endotherms was taken a s the in press. transition temperature. An optical polarizing microscope (22) Sone, M.; Harkness,B. R.;Watanabe, J.; Yamashita, T.;Torii, (Olympus BH-2) equippd with a Mettler FP-82 hot stage and T.;Hone, K.Polym. J . 1993,25, 997. a temperature programmer FP-80 was also used to observe (23) Kricheldorf, H. R.; Schwarz, G.; Domschke, A,; Linzer, V. phase transitions. X-ray diffraction data were collected using Maemmolecules lss3,26,5161. a Rigaku RINT 1500 X-ray diffractometer. Small-angle X-ray (24) Imrie, C. T.;Karasz, F. E.; Attard, G. S.Liq. Cryst. 1991,9, measurements were obtained with a Rigaku Rint 2500L X-ray 47. difiactometer. (25) Scbleeh, T.;Imrie, C. T.;Rice, D. M.; Karasz, F. E.; Attard, G. S. J . Polym. Sei., Part A: Polym. Chem. 1999, 31, 1859. Acknowledgment. We thank Messrs. Kazuhito (26) Kosaka,Y.;Kato,T.;Uryu,T. Macromhules 1994,27,2658. Hoshino and Toshiaki Hayashi of Rigaku Co. Ltd. for (27) Kosaka, Y.; Uryu, T.Macromolecules 1996,28, 870. (28) Kosaka, Y.; Kato, T.;Uryu, T.J.Polym. Sci., PartA Polym. their small-angle X-ray measurements. We also thank Chem. 1994,32,711. Mr. Kiyohisa Takizawa of Analysis Center, Dai Nippon Printing Co. Ltd., for wide-angle X-ray measurements. MA946390P
c.;
